Web materials are well known. These materials are generally planar with a thickness much smaller than the other dimensions of the material. Handling these materials during manufacturing processes presents unique challenges. Flexible web materials that are easily damaged, such as thin foils, tissue papers and the like, are particularly challenging. Wound webs, and particularly wound stretchable webs, can have fluctuations in the wound web tension throughout the length of the web. These fluctuations can be problematic as the web is unwound and transported by processing equipment in the conversion of large rolls of web material into finished products. Fluctuations in web tension can result in wrinkled or broken webs resulting in a loss of quality and/or productivity. Similarly, the velocity of a web unwinding from an out-of-round roll fluctuates over the course of each revolution due to fluctuations in the roll diameter.
Previous efforts have focused on the use of mechanical dancer systems to compensate for tension and web velocity fluctuations. These systems involve web-contacting parts that interact inertially with the web. The interaction of the webs and dancer system parts includes the transfer of energy from the web to the dancer, and from the dancer to the web. These energy transfers can create web handing problems such as web breaks and web wrinkles.
It is desired to provide a method and apparatus to facilitate the unwinding of web materials while reducing the impact of fluctuations in the wound tension of the web and also reducing the impact of the velocity fluctuations caused by rolls that are out-of-round.